Cigarette with carbon on tow filter

ABSTRACT

A cigarette comprises a tobacco rod and a carbon-on-tow filter comprising a fiber tow with flavored or unflavored carbon particles distributed throughout the tow. The carbon particles have high activity in the range of 90 to 115%, preferably 95%. As mainstream smoke is drawn through the filter, gas phase smoke constituents are removed and flavor is released when the particles are flavored. Ventilation is provided to limit the amount of tobacco being combusted during each puff and such ventilation is arranged at a location near the downstream end of the carbon-on-tow filter to lower mainstream smoke velocity through the filter. The filter achieves significant reductions in gas phase constituents of mainstream smoke, including 90% reductions or greater in at least one of 1, 3 butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, and 80% reductions or greater in acetaldehyde over extended shelf life of the cigarettes.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. 60/636,262, filed Dec. 15, 2004.

FIELD OF THE INVENTION

The present invention relates to smoking articles such as cigarettes, and in particular, to cigarettes that include filter segments comprising an adsorbent and fibrous filter materials arranged for advantageous removal of gas phase components from mainstream smoke over extended cigarette shelf life.

BACKGROUND OF THE INVENTION

Smoking articles, particularly cigarettes, generally comprise a tobacco rod of shredded tobacco (usually, in cut filler form) surrounded by a paper wrapper, and a cylindrical filter aligned in an end-to-end relationship with the tobacco rod. Typically, the filter includes a plug of cellulose acetate tow attached to the tobacco rod by tipping paper. Ventilation of mainstream smoke is achieved with a row or rows of perforations about a location along the filter. Such ventilation provides dilution of drawn mainstream smoke with ambient air to reduce the delivery of tar.

Upon lighting a cigarette, a smoker draws mainstream smoke from the coal at the lit end of the cigarette. The drawn cigarette smoke first enters the upstream end portion of the filter and then passes through the downstream portion adjacent the buccal (mouth) end of the cigarette.

Certain cigarettes have filter segments which incorporate adsorbent materials such as activated carbon, and examples of such are described in U.S. Pat. No. 2,881,770 to Tovey; U.S. Pat. No. 3,353, 543 to Sproull et al.; U.S. Pat. No. 3,101,723 to Seligman et al.; and U.S. Pat. No. 4,481,958 to Ranier et al. Certain commercially available filters have particles or granules of carbon (e.g., an activated carbon material) alone or dispersed within a cellulose acetate tow; other commercially available filters have carbon threads dispersed therein; while still other commercially available filters have so-called “plug-space-plug”, “cavity filter” or “triple filter” designs. Examples of commercially available filters are SCS IV Dual Solid Charcoal Filter and Triple Solid Charcoal Filter from Filtrona International, Ltd.; Triple Cavity Filter from Baumgartner; and ACT from Filtrona International, Ltd. See also, Clarke et al., World Tobacco, p.55 (November 1992). Detailed discussion of the properties and composition of cigarettes and filters is found in U.S. Pat. Nos. 5,404,890 and 5,568,819 to Gentry et al, the disclosures of which are hereby incorporated by reference.

Typical of prior practices with “plug-space-plug” styled cigarettes has been heretofore to locate ventilation at a location along the bed of adsorbent contained in the space, so as to achieve sufficient spacing of the ventilation holes from the buccal end of the filter. In so doing, the lips of the smoker would not occlude the ventilation holes. Such placement, however, tended to lower the filtration effectiveness of the adsorbent, because it tended to increase the velocity of the mainstream smoke in at least a portion of the absorbent bed.

Various annular configurations of filters having carbon-bearing annular filter regions are disclosed in the prior art. For example, European Patent Application No. 579,410 shows a number of cigarette embodiments having an annular carbon-bearing region surrounding either porous filtration material or an empty tubular cavity formed by a vapor phase porous membrane. Similarly, U.S. Pat. No. 3,894,545 to Crellin et al. shows various configurations of annular carbon-bearing regions surrounding a vapor phase porous membrane or a rod of carbon-bearing material surrounded by a vapor phase porous membrane.

Cigarette filter elements which incorporate carbon have the ability to remove constituents of mainstream smoke which passes therethrough. In particular, activated carbon has the propensity to reduce the levels of certain gas phase components present in the mainstream smoke, resulting in a change in the organoleptic properties of that smoke.

Despite these advantages of carbon bearing filters, heretofore they have not been widely employed. In prior arrangements it has been found that mainstream smoke from carbon filters tends to have a flavor note that is contrary to consumer preferences, and that therefore their employment in commercially offered cigarettes has not been heretofore widespread. Also, plasticizers in fiber tow filters tend to degrade certain carbon components over time and thereby reduce the efficacy of the carbon in removing gas phase component over extended shelf life of cigarettes that include such filter arrangements.

It would be desirable to provide a cigarette having a cigarette filter incorporating carbon and/or other materials capable of absorbing and/or adsorbing gas phase components present in mainstream cigarette smoke, while providing favorable absorption/adsorption, dilution and drawing characteristics.

Furthermore, it would be desirable to provide such a filter with desirable residence time in the adsorbent/absorbent-containing region while simultaneously achieving a pressure drop downstream of the dilution region and the adsorbent/absorbent so as to provide acceptable drawing characteristics of puffs of smoke having reduced gas phase components but with acceptable taste and resistance-to-draw.

SUMMARY OF THE INVENTION

In accordance with the present invention, a smoking article such as a cigarette comprises a tobacco rod and a multi-component filter comprising a fiber tow with particles of highly activated carbon on the tow. In a preferred embodiment, the activated carbon is also flavor-bearing and comprises highly, activated carbon particles on a fibrous tow. As mainstream smoke is drawn through the upstream portion of the filter, gas phase smoke constituents are removed and flavor is released from the activated carbon. Ventilation is provided to limit the amount of tobacco being combusted during each puff and such ventilation is arranged at a downstream location of most of the carbon on tow in order to lower mainstream smoke velocity through the adsorbent. It is believed that highly activated carbon particles on a cellulose acetate tow achieve significant reductions in gas phase constituents of mainstream smoke, including 90% reductions or greater in 1, 3 butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, and 80% reductions or greater in acetaldehyde.

Advantageously, the present invention addresses the desirability of achieving optimum residence times for the smoke in the region of the filter bearing the adsorbent material while also achieving favorable dilution of the smoke with ambient air and inducing an acceptable resistance to draw as is expected by most smokers.

With the foregoing and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several views illustrated in the drawing.

BRIEF DESCRIPTION OF THE DRAWING

Novel features and advantages of the present invention in addition to those mentioned above will become apparent to persons of ordinary skill in the art from a reading of the following detailed description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIG. 1 is a side elevational view of a cigarette comprising a tobacco rod and a multi-component filter including highly activated carbon particles on a fiber tow, according to the present invention, with portions thereof broken away to illustrate interior details;

FIG. 2 is a side elevational view of another cigarette comprising a tobacco rod and a multi-component filter including highly activated carbon particles on a fiber tow, according to the present invention, with portions thereof broken away to illustrate interior details;

FIG. 3 is a side elevational view of another cigarette comprising a tobacco rod and a multi-component filter including highly activated carbon particles on a fiber tow with downstream flavor addition, according to the present invention, with portions thereof broken away to illustrate interior details; and

FIG. 4 is a side elevational view of still another cigarette comprising a tobacco rod and a multi-component filter including highly activated carbon particles on a fiber tow with downstream flavor addition, according to the present invention, with portions thereof broken away to illustrate interior details.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a preferred embodiment of the present invention provides a cigarette 10 comprising a rod of smokable material 12 such as shredded tobacco and a multi-component filter 14 attached to the rod 12 with a tipping paper 16. Upon lighting of the cigarette 10, mainstream smoke is generated by and drawn from the tobacco rod 12 and through the filter 14.

Herein, the “upstream” and “downstream” relative positions between filter segments and other features are described in relation to the direction of mainstream smoke as it is drawn from the tobacco rod 12 and through the multi-component filter 14.

Preferably, the filter 14 comprises a cellulose acetate tow 18 that includes a suitable plasticizer such as triacetin with highly activated carbon particles on granules 20 distributed throughout the tow. A mouth end (mouthpiece) component 22 is downstream of the tow 18 and carbon 20.

The mouth end (buccal) component 22 is preferably in the form of a cellulose acetate plug or other suitable fibrous or webbed material of moderate to low particulate efficiency. Preferably, the particulate efficiency is low, with the denier and grand total denier being selected such that the desired total RTD of the multi-component filter 14 is achieved.

Preferably the carbon 20 on the tow 18 is in the form of granules and the like. Preferably, the carbon of the preferred embodiment is a high surface area, activated carbon, for example a coconut shell based carbon of typical ASTM mesh size used in the cigarette industry or finer. The activated carbon adsorbs constituents of mainstream smoke, particularly, those of the gas phase including aldehydes, ketones and other volatile organic compounds, and in particular 1, 3 butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, styrene, acetaldehyde and hydrogen cyanide.

With respect to the carbon particles 20, it is preferred that they have a mesh size of from 10 to 80, and more preferably a mesh size of 20 to 70. Moreover, as noted above, the carbon particles are highly activated having an overall activity in the range of 90 to 110% with a target activity of about 95% as measured by CTC (carbon tetrachloride) methodology.

The carbon particles 20 may be flavor-bearing or otherwise impregnated with a flavor so that these adsorbent particles not only remove one or more gas phase smoke constituents from mainstream smoke, but also release flavor into the mainstream smoke stream. Preferably, flavor is added to the carbon granules by spraying flavorant upon a batch of activated carbon in a mixing (tumbling) drum or alternatively in a fluidized bed with nitrogen as the fluidizing agent, wherein flavorant may then be sprayed onto the carbon in the bed. Flavor addition is done prior to distributing the carbon granules throughout the tow 18.

Preferably one or more circumferential rows of perforations 24 are formed through the tipping paper 16 at a location along the downstream end portion of the carbon on tow 18, 20. The preferred placement maximizes the distance between the buccal end of the cigarette and the perforations 24, which preferably is at least 12 mm (millimeters) or more so that a smoker's lips do not occlude the perforations 24.

Preferably, the level of ventilation is in the range of 40 to 60% and more preferably approximately 45 to 55% in a 6 mg FTC tar delivery cigarette.

It is believed that ventilation not only provides dilution of the mainstream smoke but also effects a reduction of the amount of tobacco combusted during each puff when coupled with a low particulate efficiency filter 14. Ventilation reduces drawing action on the coal and thereby reduces the amount of tobacco that is combusted during a puff. As a result, absolute quantities of smoke constituents are reduced.

Advantageously, the perforations 24 of the present invention are located at the downstream end portion of the carbon on tow filter so that mainstream smoke velocity through most of the carbon particles 20 is reduced and dwell time of the mainstream smoke amongst the carbon 20 is increased. The extra dwell time, in turn, increases the effectiveness of the activated carbon in reducing targeted mainstream smoke constituents. The smoke is diluted by ambient air passing through perforations 24 and mixing with the mainstream smoke to achieve air dilution in the approximate range of 45-65%. For example, with 50% air dilution, the flow through the cigarette upstream of the dilution perforations is reduced 50% thereby reducing the smoke velocity by 50%.

Preferably, the range carbon loading 20 on the tow 18 comprises at least 90 to greater than 120 mg (milligrams) with a target loading of approximately 120 mg. Such carbon loading provides a flavorful cigarette that achieves significant reductions in gas phase constituents of the mainstream smoke, including 90% reductions or greater in 1, 3 butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene, toluene, and 80% reductions or greater in acetaldehyde. The elevated carbon loading also assures an adequate activity level sufficient to achieve such reductions throughout the expected shelf-life of the product (up to six months or more).

With carbon activity in the range of 90 to 110% and a target of approximately 95% there is no significant adverse effect from the plasticizer (triacetin, for example) used on the fiber tow 18. When the fiber tow 18 is cellulose acetate with a triacetin plasticizer, the triacetin level may be whatever level is necessary (usually about 6%) and such level does not adversely affect the above noted percentage reductions of gas phase constituents of the mainstream smoke. With these carbon activity percentages there is no significant deactivation of the carbon over the shelf life of the cigarette products whereby the percentage reductions of gas phase constituents occurs over the entire shelf life period. Cigarettes with an extended shelf life of twelve months have about the same efficacy as one month old cigarettes.

By way of example, the length of tobacco rod 12 is preferably 49 mm, and the length of the multi-component filter 14 is preferably 34 mm. The length of the carbon on tow segment is preferably 20-26 mm and the cellulose acetate plug 8 at the end of the filter 14 is preferably 8 mm. Overall the level of tar (FTC) is preferably in the range of 6 mg with a puff count of 6 or greater.

Tobacco rod 12 may be wrapped with a convention cigarette wrapper or banded paper may be used for this purpose. Banded cigarette paper has spaced apart integrated cellulose bands 21 that encircle the finished tobacco rod of cigarette 10 to modify the mass burn rate of the cigarette so as to reduce risk of igniting a substrate if the cigarette 10 is left thereon smoldering. U.S. Pat. Nos. 5,263,999 and 5,997,691 describe banded cigarette paper, which patents are incorporated herein in their entirety.

In the preferred embodiment 10 of FIG. 1, 90 to 120 milligrams, preferably about 120 milligrams, of highly activated flavored carbon 20 in distributed throughout the fiber tow 18. The optional flavorant loading is 3 to 6 mg in the carbon 20, more preferably approximately 4 or 5 mg. As much as a 6 mg flavor system per 120 mg of carbon has shown not to have an adverse effect on constituent removal. It is to be understood that reference to a 120 mg loading of flavored carbon herein is inclusive of any flavorant. Moreover, as noted above the carbon activity is in the range of 90 to 110% with a target of approximately 95%. Despite plasticizer in the tow 18 of about 6%, the carbon on tow filter components maintains its efficacy in the removal of gas phase components over extended shelf life of cigarettes 10.

Referring to Tables I-V below, data is provided showing average percentile reductions of certain gas phase constituents in mainstream smoke achieved with test cigarettes, as described at the heading of each Table, over a commercially offered cigarette (the control). For a given test cigarette, the first column of percentiles indicate the average reductions achieved over the control initially; whereas the second and third columns show average reductions of the test cigarettes after being subjected to conditions which simulate approximately six (6) months of shelf-life and approximately twelve (12) months of shelf-life, respectively. The accelerated aging process includes the cycling of the cigarettes through high humidity conditions and low humidity, high temperature conditions for a prescribed period of time.

As the Tables show, significant reductions of gas phase, smoke constituents are achieved with 120 milligrams of carbon on tow, even in the presence of triacetin and even after significant amounts of simulated shelf life approximating one year of natural aging. TABLE I Test Cigarette: Carbon on Tow; 120 mg carbon/0% Triacetin/Unflavored Carbon/95% Activity Level Test Cigarette after Test Cigarette simulated 6 Test Cigarette after Initial: Ave. months; Ave. simulated 1 year; Gas Vapor Phase (Per Tar) Control Reduction Reduction Ave. Reduction 1,3 Butadiene FTC, ug/mg tar 97% 98% 95% Acetaldehyde FTC, ug/mg tar 95% 95% 96% Acetone FTC, ug/mg tar 76% 82% 83% Acrolein FTC, ug/mg tar 98% 98% 100%  Acrylonitrile FTC, ug/mg tar 98% 98% 96% Benzene FTC, ug/mg tar 98% 94% 97% Butyraldehyde FTC, ug/mg tar 100%  98% 99% Crotonaldehyde FTC, ug/tar 100%  100%  100%  Isoprene FTC, ug/mg tar 98% 98% 98% Propionaldehyde FTC, ug/mg tar 99% 94% 100%  Styrene FTC, ug/mg tar 96% 88% 92% Toluene FTC, ug/mg tar 98% 90% 95%

TABLE II Test Cigarette: Carbon on Tow; 120 mg carbon/3% Triacetin/Unflavored Carbon/95% Activity Level Test Cigarette after Test Cigarette simulated 6 Test Cigarette after Initial: Ave. months; Ave. simulated 1 year; Gas Vapor Phase (Per Tar) Control Reduction Reduction Ave. Reduction 1,3 Butadiene FTC, ug/mg tar 96% 98% 93% Acetaldehyde FTC, ug/mg tar 93% 94% 87% Acetone FTC, ug/mg tar 78% 82% 80% Acrolein FTC, ug/mg tar 99% 100%  95% Acrylonitrile FTC, ug/mg tar 100%  100%  96% Benzene FTC, ug/mg tar 99% 98% 97% Butyraldehyde FTC, ug/mg tar 99% 100%  93% Crotonaldehyde FTC, ug/tar 98% 100%  100%  Isoprene FTC, ug/mg tar 98% 99% 97% Propionaldehyde FTC, ug/mg tar 99% 100%  95% Styrene FTC, ug/mg tar 100%  96% 96% Toluene FTC, ug/mg tar 99% 98% 98%

TABLE III Test Cigarette: Carbon on Tow; 120 mg carbon/6% Triacetin/Unflavored Carbon/95% Activity Level Test Cigarette after Test Cigarette simulated 6 Test Cigarette after Initial; Ave. months; Ave. simulated 1 year; Gas Vapor Phase (Per Tar) Control Reduction Reduction Ave. Reduction 1,3 Butadiene FTC, ug/mg tar 92% 97% 93% Acetaldehyde FTC, ug/mg tar 91% 93% 87% Acetone FTC, ug/mg tar 79% 84% 80% Acrolein FTC, ug/mg tar 98% 97% 95% Acrylonitrile FTC, ug/mg tar 96% 100%  96% Benzene FTC, ug/mg tar 94% 98% 97% Butyraldehyde FTC, ug/mg tar 96% 96% 93% Crotonaldehyde FTC, ug/tar 97% 100%  100%  Isoprene FTC, ug/mg tar 96% 98% 97% Propionaldehyde FTC, ug/mg tar 97% 99% 95% Styrene FTC, ug/mg tar 86% 100%  96% Toluene FTC, ug/mg tar 90% 99% 98%

TABLE IV Test Cigarette: Carbon on Tow; 120 mg carbon/0% Triacetin/Flavored Carbon/95% Activity Level Test Cigarette after Test Cigarette simulated 6 Test Cigarette after Initial: Ave. months; Ave. simulated 1 year; Gas Vapor Phase (Per Tar) Control Reduction Reduction Ave. Reduction 1,3 Butadiene FTC, ug/mg tar 95% 93% 91% Acetaldehyde FTC, ug/mg tar 91% 89% 91% Acetone FTC, ug/mg tar 83% 82% 74% Acrolein FTC, ug/mg tar 100%  100%  100%  Acrylonitrile FTC, ug/mg tar 95% 95% 94% Benzene FTC, ug/mg tar 95% 96% 93% Butyraldehyde FTC, ug/mg tar 98% 95% 97% Crotonaldehyde FTC, ug/tar 100%  100%  100%  Isoprene FTC, ug/mg tar 97% 96% 95% Propionaldehyde FTC, ug/mg tar 100%  100%  100%  Styrene FTC, ug/mg tar 90% 97% 84% Toluene FTC, ug/mg tar 93% 97% 88%

TABLE V Test Cigarette: Carbon on Tow; 120 mg carbon/6% Triacetin/Flavored Carbon/95% Activity Level Test Cigarette after Test Cigarette simulated 6 Test Cigarette after Initial: Ave. months; Ave. simulated 1 year; Gas Vapor Phase (Per Tar) Control Reduction Reduction Ave. Reduction 1,3 Butadiene FTC, ug/mg tar  97% 85% 87% Acetaldehyde FTC, ug/mg tar  94% 84% 84% Acetone FTC, ug/mg tar  89% 82% 76% Acrolein FTC, ug/mg tar 100% 93% 100%  Acrylonitrile FTC, ug/mg tar 100% 92% 96% Benzene FTC, ug/mg tar 100% 95% 96% Butyraldehyde FTC, ug/mg tar 100% 91% 100%  Crotonaldehyde FTC, ug/tar 100% 100%  100%  Isoprene FTC, ug/mg tar  99% 94% 95% Propionaldehyde FTC, ug/mg tar 100% 93% 92% Styrene FTC, ug/mg tar 100% 97% 96% Toluene FTC, ug/mg tar 100% 97% 97%

FIG. 2 shows a cigarette 10A with a shorter tow 18A and reduced loading of carbon particles 20A distributed amongst the tow. The carbon loading is about 75 milligrams and the carbon is unflavored. Activity of the carbon is within the range of 90 to 115% with a target of approximately 95%.

Referring now to FIGS. 3 and 4, alternate preferred embodiments include cigarettes 10B, 10C which include a carbon-on-tow filter plug 18 having a carbon loading of approximately 75 to 120 milligrams or greater of elevated activity level (90 to 110% with a target level of approximately 95%), more preferably approximately 120 milligrams of such carbon in cigarette 10B and approximately 75 milligrams of such carbon in cigarette 10C, both preferably without flavors. Approximately 90 mg carbon is a preferred amount. In these embodiments, the filters further include a flavor release element 32, 32A at a location downstream of the carbon-on-tow (in the sense of direction as mainstream smoke is drawn through the cigarette), such as in FIG. 3, a filter plug 32 having a flavor-bearing yarn 33 therein (such as described in commonly assigned U.S. Pat. No. 6,761,174) or a bed of flavor-releasing particles 35 as shown in FIG. 4, which particles may be arranged in the space of a plug-space-plug arrangement at element 32 or as a plug of fibrous tow with flavor-releasing particles disposed therein.

With the elevated carbon loading and elevated carbon activity levels, these cigarettes 10B, 10C of FIGS. 3 and 4 offer enhanced capability to remove gas phase smoke constituents, acceptable shelf-life and favorable organoleptic properties.

Moreover, the present invention may be practiced with cigarettes of various circumferences, narrow cigarettes as well as wide. Also, while the present invention is preferably practiced with unflavored tobacco rods, flavored tobacco material is also contemplated. 

1. A cigarette comprising a tobacco rod and a carbon-on-tow filter comprising a fiber tow with carbon particles distributed amongst the tow, the carbon-on-tow filter being constructed and arranged to substantially remove at least one smoke constituent from mainstream tobacco smoke as mainstream smoke is drawn through the filter, and the carbon particles having an activity in the range of 90 to 115%.
 2. The cigarette as in claim 1 wherein the carbon comprises approximately 75 to 120 milligrams or greater.
 3. The cigarette as in claim 2 wherein the carbon particles are flavored.
 4. The cigarette as in claim 1 wherein the carbon comprises approximately 120 milligrams.
 5. The cigarette as in claim 4 wherein the carbon particles are flavored.
 6. The cigarette as in claim 1 wherein the activity of the carbon particles is approximately 95%.
 7. The cigarette as in claim 1 wherein the filter includes ventilation and the ventilation is in the range of 45 to 55%, and wherein a mouth end filter component is downstream of the carbon-on-tow filter component.
 8. The cigarette as in claim 7 wherein the ventilation comprises at least one circumferential row of perforations through a tipping paper, the tipping paper attaching the carbon-on-tow filter to the tobacco rod.
 9. The cigarette as in claim 8 wherein the ventilation is located at least 12 mm from a buccal end of the cigarette.
 10. The cigarette as in claim 1, wherein the carbon-on-tow filter achieves significant reductions in gas phase constituents of the mainstream smoke, including 90% reductions or greater in at least one of 1,3 butadiene, acrolein, isoprene, propionaldehyde, acrylonitrile, benzene and toluene over an extended shelf life of at least six months.
 10. The cigarette as in claim 1 wherein the carbon-on-tow filter achieves significant reductions in gas phase constituents of the mainstream smoke, including 80% reductions or greater of acetaldehyde.
 11. The cigarette as in claim 1 wherein the filter includes a flavor release element located downstream of the carbon-on-tow. 